How do I delete a picture or video I've uploaded?

Navigate to the picture or video you want to delete (make sure you're looking at the enlarged picture or playable video). On the right side of the page, click on the "delete" link. Once you confirm you want to delete the file presto, it is gone, gone, gone...

If the picture is your avatar, you will need to change your avatar to a different picture, then you can delete it.